Control device having buttons with multiple-level backlighting

ABSTRACT

A control device may have a plurality of buttons that may be backlit to multiple levels, such as first, second, and third adjacent buttons positioned in order, and first, second, and third LEDs positioned to illuminate a respective button. The control device may be configured to illuminate the first LED to a first LED illumination intensity to illuminate the respective button to a first surface illumination intensity; illuminate the third LED to a second LED illumination intensity to illuminate the respective button to a second surface illumination intensity; and illuminate the second LED to a third LED illumination intensity to illuminate the respective button to the second surface illumination intensity. The third LED illumination intensity may be less than the second LED illumination intensity, which may be less than the first LED illumination intensity, and the second surface illumination intensity may be less than the first surface illumination intensity.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No. 15/680,516, filed Aug. 18, 2017, which is a continuation of U.S. patent application Ser. No. 14/850,315, filed Sep. 10, 2015, now U.S. Pat. No. 9,763,302, issued Sep. 12, 2017, which claims the benefit of U.S. Provisional Application No. 62/166,204, filed May 26, 2015, and U.S. Provisional Application No. 62/048,658, filed Sep. 10, 2014, which are incorporated by reference herein as if fully set forth.

BACKGROUND

Home automation systems, which have become increasing popular, may be used by homeowners to integrate and control multiple electrical and/or electronic devices in their house. For example, a homeowner may connect appliances, lights, blinds, thermostats, cable or satellite boxes, security systems, telecommunication systems, and the like to each other via a wireless network. The homeowner may control these devices using a controller, a remote control device (e.g., such as a wall-mounted keypad), or user interface provided via a phone, a tablet, a computer, and the like directly connected to the network or remotely connected via the Internet. These devices may communicate with each other and the controller to, for example, improve their efficiency, their convenience, and/or their usability.

A control device may include a plurality of buttons where, for example, each button may control a different device and/or control a device to a preset level or intensity. It may be desirable to backlight the buttons of the control device so that a user may easily see them if the room is dark. Backlighting may also be used to indicate which of the buttons is currently set, for example, by setting that button to a higher intensity level than the others. However, variables such as ambient lighting conditions, button color, location and configuration of the control device, etc. may adversely affect how the backlighting is perceived by a user, for example, by reducing the readability of the buttons, reducing the contrast between selected and unselected buttons, and/or the like. As such, there exists a need for a backlight solution that provides consistent backlighting intensities and prevents bleed through of light between buttons regardless of the ambient light in the room, the color of the buttons, the configuration of the control device and/or the like.

SUMMARY

The present disclosure relates to a load control system for controlling the amount of power delivered to an electrical load, such as a lighting load, and more particularly, to a keypad having buttons with backlighting for use in a load control system.

A control device may include one or more buttons and have multiple-level backlighting. For example, the control device may include a control circuit, a first button, a second button, a third button, a first LED, a second LED, and a third LED. The first, second, and third LEDs may be configured to illuminate at least a portion of a respective one of the first, second, and third buttons. The control circuit may be electrically coupled to the first, second, and third buttons and the first, second, and third LEDs. The control circuit may be configured to illuminate the first LED to a first LED illumination intensity to illuminate the first button to approximately a first surface illumination intensity, illuminate the third LED to a second LED illumination intensity to illuminate the third button to approximately a second surface illumination intensity, and illuminate the second LED to a third LED illumination intensity to illuminate the second button to approximately the second surface illumination intensity. The second LED illumination intensity may be less than the first LED illumination intensity. The third LED illumination intensity may be less than the second LED illumination intensity, and the second surface illumination intensity may be less than the first surface illumination intensity.

The control device may include an ambient light detector. The ambient light detector may be configured to generate an ambient light detect signal. The control circuit may be configured to receive the ambient light detect signal and, based on the ambient light detect signal, determine an ambient light level in the room in which the control device is installed. One or more of the first LED illumination intensity, the second LED illumination intensity, or the third LED illumination intensity may be based at least in part on the ambient light level. The control circuit may be configured to determine illumination caused by at least one of the first LED, the second LED, or the third LED, and determine the ambient light level based on the illumination caused by at least one of the first LED, the second LED, or the third LED, for example, to compensate for the illumination of one or more LEDs in the ambient light detect signal. The control circuit may be configured to detect a change in the ambient light level, and adjust the first LED illumination intensity, the second LED illumination intensity, and/or the third LED illumination intensity based on the change in the ambient light level.

The first button may include indicia (e.g., text), and the second button may be closer to the indicia than the third button. The first button may be in a selected state. The first LED illumination intensity may be determined based on an active adjustment curve DC_(ACTIVE), and the second LED illumination intensity and the third LED illumination intensity are based on an inactive adjustment curve DC_(INACTIVE).

The control device may include a communication circuit configured to transmit control signals. For example, the control circuit may be electrically coupled to the communication circuit, and the control circuit may be configured to control at least one electrical load in response to at least one of the first button, the second button, or the third button receiving a user input. The control device may be configured to be electrically connected to an AC power source.

A control device may comprise a plurality of buttons, a plurality of LEDs, and a control circuit. Each of the LEDs may be configured to illuminate at least a portion of a respective button of the plurality of buttons. The control circuit may be electrically coupled to the plurality of buttons and the plurality of LEDs. The control circuit may be configured to determine that a button of the plurality of buttons is in a selected state. The control circuit may be configured to illuminate the LED of the selected button to a first LED illumination intensity to illuminate at least a portion of the selected button to approximately a first surface illumination intensity based on the button being in the selected state. The control circuit may be configured to illuminate the LEDs of each of the remaining buttons to respective illumination intensities to illuminate at least a portion of each of the remaining buttons to approximately a second surface illumination intensity. The second surface illumination intensity may be less than the first surface illumination intensity. The respective illumination intensities of the LEDs of each of the remaining buttons may be based on the relative position of each of the remaining plurality of buttons to the selected button. For example, the illumination intensity of an LED of a button that is closer to the selected button may be less than the illumination intensity of an LED of a button that is further from the selected button.

The control device may include an ambient light detector. The ambient light detector may be configured to generate an ambient light detect signal. The control circuit may be configured to receive the ambient light detect signal and, based on the ambient light detect signal, determine an ambient light level in the room in which the control device is installed. The first LED illumination intensity and the LED illumination intensities of the remaining buttons may be based at least in part on the ambient light level. The control circuit may be configured to determine illumination caused by one or more of the plurality of LEDs, and determine the ambient light level based on the illumination caused by the one or more of the plurality of LEDs.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an example control device (e.g., a wall-mounted keypad) for use in a load control system for controlling the amount of power delivered to one or more electrical loads.

FIG. 2 is a simplified block diagram of an example control device.

FIG. 3 is a simplified flowchart of an example backlighting procedure.

FIG. 4 illustrates example adjustment curves for adjusting duty cycles of currents conducted through light-emitting diodes illuminating buttons of a control device in response to a measured ambient light level on a linear scale.

FIG. 5 illustrates example adjustment curves for adjusting duty cycles of currents conducted through light-emitting diodes illuminating buttons of a control device in response to a measured ambient light level on a logarithmic scale.

FIG. 6 is a simplified flowchart of another example backlighting procedure.

DETAILED DESCRIPTION

FIG. 1 is a perspective view of an example control device (e.g., a wall-mounted keypad 100) for use in a load control system for controlling the amount of power delivered to one or more electrical loads (e.g., lighting loads). The keypad 100 may comprise a faceplate 102 and a plurality of buttons 104 (e.g., four buttons). The plurality of buttons 104 may be received through an opening 106 of the faceplate 102. In one or more examples, the faceplate 102 and/or the buttons 104 may have a metallic surface. The faceplate 102 may be configured to be attached (e.g., snapped) to an adapter 108, which may be attached (e.g., using screws) to an enclosure (not shown) that houses the electrical circuitry of the control device. The keypad 100 may be electrically connected to an alternating-current (AC) power source (not shown) for receiving power.

The keypad 100 may be configured to transmit a digital message to one or more external load control device via a communication link for controlling respective electrical loads. The communication link may comprise a wired communication link or a wireless communication link, such as a radio-frequency (RF) communication link. Alternatively and/or additionally, the keypad 100 may comprise an internal load control circuit for controlling the power delivered to one or more electrical loads. For example, the keypad 100 may be configured to control AC power delivered from the AC power source to one or more electrical loads. Examples of load control systems having remote control devices, such as the keypad 100, are described in greater detail in commonly-assigned U.S. Pat. No. 6,803,728, issued Oct. 12, 2004, entitled SYSTEM FOR CONTROL OF DEVICES, and U.S. Patent Application Publication No. 2014/0001977, published Jan. 2, 2014, entitled LOAD CONTROL SYSTEM HAVING INDEPENDENTLY-CONTROLLED UNITS RESPONSIVE TO A BROADCAST CONTROLLER, the entire disclosures of which are hereby incorporated by reference.

The button 104 may comprise indicia, such as text 120, for indicating a preset (e.g., a lighting scene) or command that may be transmitted in response to an actuation of the button 104. Alternatively or additionally, the indicia on the button 104 may comprise an icon or symbol. A preset may relate to a particular mode of operation of an electrical load. For example, if the electrical load is a lighting load, the preset may relate to a particular lighting intensity level of the lighting load. For instance, a “morning” preset may set a lighting load at a medium-high lighting intensity level (e.g., 70% intensity), a “day” preset may set a lighting load at a high lighting intensity level (e.g., 100% intensity, or full on), an “evening” preset may set the lighting load at a medium-low intensity level (e.g., 30% intensity), and a “night” preset may set the lighting load at a low lighting intensity level (e.g., 10% intensity). The one or more presets or commands may be preconfigured and/or adjusted by the user through a commissioning mode of the keypad 100.

The buttons 104 may be backlit to allow the indicia to be read in a wide range of ambient light levels. Each button 104 may be made of a translucent (e.g., transparent, clear, and/or diffusive) material. For example, the buttons 104 may be made of plastic. The buttons 104 may be illuminated by one or more light sources (e.g., LEDs) located behind and/or to the side of each button (e.g., inside of the keypad 100). In addition, the buttons 104 may each have a metallic surface. Specifically, each button 104 may have a translucent body (not shown) and an opaque material, e.g., a metallic sheet (not shown), adhered to a front surface of the body. The text 120 may be etched into the metallic sheet of each button 104 (e.g., through a machining process, laser cutting, photo-etching, or other metal-removal process). The illumination from the LEDs may shine through the translucent body, but not through the metallic sheet, such that the text 120 of each button (e.g., that is etched away from the metallic sheet) is illuminated.

Alternatively or additionally, the buttons 104 may be coated with another type of opaque material, such as paint, and the text 120 may be etched into the paint. For example, the body 112 of the button 104 may be made of a translucent material, such as glass. The opaque material (e.g., such as paint) may be coated onto the rear surface 118 of the body 110 and the text 118 may be etched into paint on the rear surface of the body. Moreover, the faceplate 102 of the keypad 100 may comprise a metallic sheet and text or other indicia etched into the metallic plate and backlit by LEDs located behind the faceplate.

The keypad 100 may operate to backlight the buttons 104, such that the text 120 of a selected preset (e.g., an “active” preset) is illuminated to an active surface illumination intensity L_(SUR1), and the text of each of the other presets (e.g., “inactive” presets) is illuminated to an inactive surface illumination intensity L_(SUR2). The active surface illumination intensity L_(SUR1) may be greater than the inactive surface illumination intensity L_(SUR2), such that a user may identify which of the presets is selected based upon the intensity of the illumination of the text 120.

The ambient light level in the room in which the keypad 100 is installed may affect a user's ability to read the text 120 on the buttons 104. For example, if the contrast between the brightness of the illuminated text 120 and the brightness of the adjacent surface of the button 104 is too low, the illuminated text may appear washed out to the user. Factors such as the ambient light, the color of the buttons, the color of the walls, ceilings, and floors in the room, and the like may contribute. As such, the user may not be able to identify which of the presets is selected (e.g., “active”) based on the intensity of the illumination of the text 120.

Accordingly, the keypad 100 may comprise an ambient light detection circuit, which may be located inside of the keypad and may be configured to measure the ambient light level in the room in which the keypad 100 is installed. For example, the keypad 100 may comprise an opening 130 in the adapter 108 through which the ambient light detection circuit may receive light to make a determination of the ambient light level in the room. Alternatively or additionally, the keypad 100 may comprise an opening in the faceplate 102 and/or one or more of the buttons 104 for allowing the ambient light detection circuit to receive light. In addition, the ambient light detection circuit may be configured to receive light through the gaps between the buttons 104 and/or through the material of the buttons. The ambient light detection circuit may also be positioned behind a semi-transparent or dark window and may be configured to receive light through the window. The keypad 100 may comprise a light pipe for directing light from outside of the keypad to the ambient light detection circuit.

The keypad 100 may be configured to adjust the active and inactive surface illumination intensities L_(SUR1), L_(SUR2) in response to the measured ambient light level. For example, the keypad 100 may be configured to increase the active and inactive surface illumination intensities L_(SUR1), L_(SUR2) if the ambient light level increases, and decrease the active and inactive

FIG. 2 is a simplified block diagram of an example control device 200 that may be deployed as, for example, the keypad 100 shown in FIG. 1. The control device 200 may comprise a control circuit 210, which may include one or more of a processor (e.g., a microprocessor), a microcontroller, a programmable logic device (PLD), a field programmable gate array (FPGA), an application specific integrated circuit (ASIC), or any suitable processing device. The control device 200 may comprise one or more actuators 212 (e.g., mechanical tactile switches), which may be actuated in response to actuations of the buttons 104. The control circuit 200 may be coupled to the actuators 212 for receiving user inputs.

The control device 200 may further comprise a communication circuit 214, such as, a wired communication circuit or a wireless communication circuit (e.g., an RF transmitter coupled to an antenna for transmitting RF signals). The control circuit 210 may be coupled to the communication circuit 214 for transmitting digital messages in response to actuations of the actuators. Alternatively or additionally, the communication circuit 214 may include an RF receiver for receiving RF signals, an RF transceiver for transmitting and receiving RF signals, and/or an infrared (IR) transmitter for transmitter IR signals. In addition, the control circuit 210 may be configured to receive a digital message including, for example, a selected preset and/or the status of an electrical load controlled by an external load control device.

The control device 200 may also include a memory 216 communicatively coupled to the control circuit 210. The control circuit 210 may be configured to use the memory 216 for the storage and/or retrieval of, for example, commands and/or preset information to transmit in response to actuations of the buttons 104. The memory 216 may be implemented as an external integrated circuit (IC) or as an internal circuit of the control circuit 210. The memory 216 may include one or more components of volatile and/or non-volatile memory, in any combination.

The control device 200 may also comprise a power supply 218 for generating a direct-current (DC) supply voltage V_(CC) for powering the control circuit 210, the communication circuit 214, the memory 216, and the other low-voltage circuitry of the control device. The power supply 218 may be coupled to an alternating-current (AC) power source or an external DC power source via electrical connections 219. Alternatively or additionally, the control device 200 may comprise an internal power source (e.g., one or more batteries) in place of or for supplying power to the power supply 218.

The control device 200 may further comprise a backlighting circuit 220 for illuminating indicia on one or more buttons (e.g., the buttons 104 of the keypad 100). For example, the backlighting circuit 220 may comprise four LEDs 222 coupled to respective ports on the control circuit 210 via respective resistors 224. The control circuit 210 is configured to individually turn each LED 222 on by pulling the respective port low towards circuit common, such that the LED is coupled between the supply voltage V_(CC) and circuit common through the respective resistor 224. The control circuit 210 may be configured to dim the illumination of each LED 222, e.g., by pulse-width modulating the LED current conducted through each LED and adjusting a duty cycle DC_(LED) of the respective pulse-width modulated LED current.

While the control device 200 shown in FIG. 2 has one LED 222 for illuminating each of the buttons 104, each LED illustrated in FIG. 2 may comprise one or more LEDs coupled in series or parallel. For example, each LED 222 in FIG. 2 may comprise four LEDs coupled in series. For example, the LEDs 222 may comprise white LEDs, e.g., part number LTW-C191DS5-LR, manufactured by LITE-ON. Each of the resistors 224 coupled in series with the respective LEDs 222 may have a resistance sized such that the maximum average magnitude of LED current may be approximately 20 mA, for example.

The control circuit 210 may be configured to backlight the buttons 104, such that the text 120 of a specific button (e.g., a button having text indicating a selected preset, herein referred to as “the selected button”) is illuminated to an active surface illumination intensity L_(SUR1), and the text of each of the other buttons (e.g., the non-selected or inactive buttons) is illuminated to an inactive surface illumination intensity L_(SUR2). The inactive surface illumination intensity L_(SUR2) may be less than the active surface illumination intensity L_(SUR1). To illuminate the text of one of the buttons 104 to the active surface illumination intensity L_(SUR1), the control circuit 210 may pulse-width modulate the LED current through the LED 222 behind the button using a first LED duty cycle DC_(LED1) to cause the respective LED 222 to illuminate to a first LED illumination intensity L_(LED1). To illuminate the text of one of the buttons 104 to the inactive surface illumination intensity L_(SUR2), the control circuit 210 may pulse-width modulate the LED current through the LED 222 behind the button using a second LED duty cycle DC_(LED2) (e.g., approximately 15%) to cause the respective LED 222 to illuminate to a second LED illumination intensity L_(LED2), which may be less that the first LED illumination intensity L_(LED1).

The control device 200 may further comprise an ambient light detector 230 (e.g., an ambient light detection circuit) for measuring an ambient light level L_(AMB) in the room in which the control device 200 is installed. The ambient light detector 230 may generate an ambient light detect signal V_(AMB), which may indicate the ambient light level L_(AMB) and may be received by the control circuit 210. The control circuit 210 may receive the ambient light detect signal V_(AMB) and determine the ambient light level L_(AMB) accordingly. The ambient light level L_(AMB) may include, for example, illumination from daylight, one or more lighting loads in the room, and/or the like.

The control circuit 210 may be configured to adjust the first and second LED illumination intensities L_(LED1), L_(LED2) in response to the measured ambient light level L_(AMB) as determined from the ambient light detect signal V_(AMB). For example, the control circuit 210 may be configured to adjust the first duty cycle DC_(LED1) of the LED current through the LED 222 behind the button having the active preset in response to the measured ambient light level L_(AMB), and to adjust the second duty cycle DC_(LED2) of the LED current through each of the LEDs 222 behind the buttons having the inactive presets in response to the measured ambient light level L_(AMB). For example, the control circuit 210 may be configured to increase the first and second LED illumination intensities L_(LED1), L_(LED2) to increase the active and inactive surface illumination intensities L_(SUR1), L_(SUR2) if the ambient light level increases. The control circuit 210 may be configured to decrease the first and second LED illumination intensities L_(LED1), L_(LED2) to decrease the active and inactive surface illumination intensities L_(SUR1), L_(SUR2) if the ambient light level decreases.

The control device 200 may account for reflection of light generated by the LEDs 222 of the buttons when determining the ambient light level L_(AMB). For example, illumination from the LEDs 222 of the buttons may reflect off the wall, floor, ceiling, control device 200 itself, etc. and alter the measured ambient light level L_(AMB). This may depend on the particular installation of the control device 200, the color of the ceiling, floor, and/or wall of the room, etc. For example, if an opening for the ambient light detector 230 is provided along the bottom of the faceplate (e.g., as is the case with opening 130 in FIG. 1), the LED 222 behind the bottom button may cause inaccuracies in the ambient light level L_(AMB) calculated by the ambient light detector 230. In some instances, the illumination caused by the LEDs 222 may cause runaway in the ambient light level L_(AMB) (e.g., the ambient light detector 230 may calculate the ambient light to include illumination from the LED 222, the control circuit 210 may increase the LED intensity to compensate for the ambient light, which in turn may increase the measured ambient light level L_(AMB)).

Accordingly, the control device 200 may calculate the part of the ambient light level L_(AMB) caused by the LEDs 222 and remove the light caused by the LEDs 222 from the ambient light level L_(AMB). For example, the control device 200 may calculate the part of the ambient light level L_(AMB) caused by the LEDs 222 using the intensity level of the LEDs (e.g., which is known to the control circuit 210) and/or the degree of bleed and/or reflection of the respective LEDs 222 (e.g., which may be preconfigured in the control circuit 210 or determined during a commissioning step). Alternatively or additionally, the control device 200 may comprise an isolation element, such as light blocking foam, between the ambient light detector 230 and the LEDs 222 to prevent and/or reduce inaccuracies in the ambient light level L_(AMB) caused by the illumination of the LEDs 222.

Illumination from the LED 222 behind the selected button may affect the surface illumination intensity of the adjacent buttons such that, for example, the surface illumination intensity of the adjacent buttons is not equal to the second surface illumination intensity L_(SUR2). For example, the illumination from the LED 222 behind the selected button may shine directly on and/or be reflected or refracted onto the rear surfaces of the bodies of the adjacent buttons and cause the surface illumination intensity of the adjacent buttons to increase (e.g., and in turn, not be equal to the inactive surface illumination intensity L_(SUR2)). Accordingly, the control device 200 may be configured to adjust the illumination intensity of an LED 222 of a button based on its relative proximity to the selected button, for example, to cause all of the buttons other than the selected button to be illuminated to the inactive illumination intensity L_(SUR2). For example, the control circuit 210 may be configured to decrease the intensities of the LEDs 222 of the buttons next to the selected button below the inactive LED illumination intensity L_(LED2), such that the resulting illumination intensity of the text on the buttons is equal to the inactive surface illumination intensity L_(SUR2).

As described, the control device 200 may be configured to adjust the illumination intensity of an LED 222 of a button based on its relative proximity to the selected button, for example, to ensure that the buttons other than the selected button are illuminated to the inactive illumination intensity L_(SUR2). The control device 200 may utilize correction factors to determine the intensities of the LEDs 222 of the buttons other than the selected button. The correction factors may vary based on the intensity of the LEDs 222 of the selected and unselected buttons. For example, the ratio between the intensities of the selected and unselected buttons may be greater at lower light levels (e.g., up to a 15× difference) than at higher light levels (e.g., as low as a 3× difference), for example, because the human focal system may have less ability to differentiate between light at low intensity levels. And the ratios may be configured based on external factors, such as the color of the walls, ceiling, floors, keypad, etc.

The control device 200 may use a constant percentage as a correction factor to determine the intensities of the LEDs 222 of the buttons based on their relative position with respect to the selected button. In one or more embodiments, the control device 200 may perform a closed-loop commission operation (e.g., when the control device 200 is first installed) to determine one or more correction factors to used when determining the intensities of the LEDs 222 of the buttons based on their relative position to the selected button. Then during normal operation, the control circuit 210 may operate in an open-loop mode. When performing the closed-loop operation, the control device 200 may store each of the variables used when determining the correction factors (e.g., which button is the selected button, the various loads being on, the ambient light level L_(AMB), etc.). Alternatively or additionally, commissioning may be performed via the use of a smart phone. For example, a picture of each combination of variables (e.g., with each button being the selected button) may be taken by a smart phone, sent to the cloud, and the control device 200 may receive one or more correction factors accordingly. In one or more examples, the control device 200 may use the ambient light level L_(AMB) to determine and/or refine the intensities of the LEDs 222 of the buttons next to the selected button.

The specific location of the indicia on the buttons may affect how and which buttons are affected by the illumination from the LEDs 222 behind the selected button. For example, the text on the buttons 104 may be located towards the topside of the buttons, such as is shown in FIG. 1. In such instances, the illumination from the LED 222 behind the selected button may have a greater effect on the surface illumination of the button right above the selected button than the button below the selected button. For example, the LED 222 behind the selected button may cause a first predetermined amount of change Δ_(LED1) (e.g., approximately 9%) on the button below the selected button and a second predetermined amount of change Δ_(LED2) (e.g., approximately 15%) on the button above the selected button.

Accordingly, the control circuit 210 may be configured to adjust the illumination intensity of an LED 222 of a non-selected button based on its relative proximity to the indicia of the selected button. For example, the control circuit 210 may be configured to control the LED 222 of the button closest to the text of the selected button to an illumination intensity that is less than the illumination intensity of the LED 222 of the button that is further from the text of the selected button (e.g., to compensate for any reflection or fraction of light from the LED 222 of the selected button). For example, assuming the text is located towards the topside of the buttons, the control circuit 210 may be configured to control the LED 222 of the button below the selected button to a third LED illumination intensity L_(LED3) and to control the LED 22 of the button above the selected button to a fourth LED illumination intensity L_(LED4) that is less than the third LED illumination intensity L_(LED3). For example, the control circuit 210 may be configured to control the illumination of each of the LEDs to the third and fourth LED illumination intensities L_(LED3), L_(LED4) by controlling the LED current through the respective LED using respective third and fourth LED duty cycles DC_(LED3), DC_(LED4) (e.g., approximately 5% and 1%, respectively). If the text on the buttons 104 is located towards the center of the buttons, the control circuit 210 may be configured to control the LEDs of the buttons below and above the selected button to the same LED illumination intensity.

The example values of the duty cycles used to control the illumination of the LEDs 222 to the first, second, third, and fourth LED illumination intensities L_(LED1)-L_(LED4) provided herein are examples values, which for example, may be used when the bodies 110 of the buttons 104 are made from a translucent plastic. The values of the LED illumination intensities may vary depending upon the material of the buttons 104, the size, shape, and location of the indicia on the buttons 104, the number and size of LEDs 222, and/or the like.

The control device 200 may compensate for the degradation of the LEDs over their lifecycle. For example, using the ambient light detector 230, the control device 200 may determine that the light output from the LEDs of each button does not correspond to their set LED illumination intensity L_(LED). The control device 200 may determine the actual light output of the LEDs based on the set LED illumination intensity L_(LED) and the ambient light level L_(AMB) measured by the ambient light detector 230. For example, the control device 200 may be placed in a commissioning mode (e.g., when the control device 200 is first installed), where the control device 200 determines the ambient light level L_(AMB) with the LEDs off, then turns the LEDs behind each button on and measures the difference in ambient light level L_(AMB) to determine a baseline value for the LED illumination intensity L_(LED) of the LEDs of each button. Using that baseline value, the control device 200 may determine whether the actual light output from the LEDs of each button corresponds to the set LED illumination intensity L_(LED). As the actual light output of the LEDs degrades over time, the control device 200 may increase the LED illumination intensity L_(LED) to compensate for the degradation of the LEDs. The control device 200 may perform this test periodically (e.g., once every predetermined amount of time, such as every six months), when commissioned by a user, and/or the like.

FIG. 3 is a simplified flowchart of an example backlighting procedure 300 that may be executed periodically by the control circuit 210 for backlighting the buttons 104. At 310, the control circuit 210 may set a selected-button number N_(SEL) to be equal to the presently selected button (e.g., due to the presently selected preset or scene). For example, the number N_(SEL) may be one for the top button, two for the second button, three for the third button, and four for the bottom button of the keypad 100 shown in FIG. 1. In other words, if the Evening button is the selected button, the control circuit 210 will set the number N_(SEL) to three at 310. During the backlighting procedure 300, the control circuit 210 may step through the LEDs 222 behind each of the buttons 104 and determine the correct LED illumination intensity for each of the buttons. The control circuit 210 may use a variable n for stepping through the LEDs during the backlighting procedure 300. At 312, the control circuit 210 may initialize the variable n to one.

If the variable n is equal to the selected-button number N_(SEL) at 314 (e.g., the present button is the selected button), the control circuit 210 may control the nth LED to the first LED illumination intensity L_(LED1) at 316. If the variable n is equal to the selected-button number N_(SEL) plus one at 318 (e.g., the button below the selected button), the control circuit 210 control the nth LED to the third LED illumination intensity L_(LED3) at 320. If the variable n is equal to the selected-button number N_(SEL) minus one at 322 (e.g., the button above the selected button), the control circuit 210 control the nth LED to the fourth LED illumination intensity L_(LED4) at 324. The fourth LED illumination intensity L_(LED4) may be less than the third LED illumination intensity L_(LED3), for example, if the indicia on the buttons is located near the topside of the buttons as shown in FIG. 1. If the variable n is not equal to the selected-button number N_(SEL) minus one at 322, the control circuit 210 may control the nth LED to the second LED illumination intensity L_(LED2) at 326. In one or more examples, if the variable n is not equal to the selected-button number N_(SEL) minus one at 322, the control circuit 210 may control the nth LED to an LED illumination intensity L_(LED) that is dependent upon the button's relative location with respect to the selected-button at 326.

After setting the LED illumination intensity at 316, 320, 324, and 326, the control circuit 210 may determine if the variable n is equal to a maximum number N_(MAX) (e.g., the number of buttons 104 on the keypad 100) at 328. If the variable n is not equal to the maximum number N_(MAX) at 328, the control circuit 210 increments the variable n by one at 330, and the procedure 300 loops around the set the LED illumination intensity for the next LED. If the variable n is equal to the maximum number N_(MAX) at 328, the procedure 300 exits.

As previously mentioned, the ambient light level in the room in which the keypad is installed may affect a user's ability to read the text on the buttons. Accordingly, the control circuit 210 may be configured to adjust the first, second, third, and fourth LED illumination intensities L_(LED1), L_(LED2), L_(LED3), L_(LED4) by adjusting the respective duty cycle DC_(LED1), DC_(LED2), DC_(LED3), DC_(LED4) in response to the ambient light level L_(AMB) measured by the ambient light detector circuit 230. The control circuit 210 may adjust the selected (e.g., or active) button according to one adjustment curve and the unselected (e.g., or inactive) buttons according to a different adjustment curve. For example, the control circuit 210 may be configured to adjust the first duty cycle DC_(LED1) of the LED current through the LED behind the button having the active preset in response to the measured ambient light level L_(AMB) according an active LED adjustment curve DC_(ACTIVE), and to adjust the second duty cycle DC_(LED2) of the LED current through each of the LEDs behind the buttons having the inactive presets in response to the measured ambient light level L_(AMB) according an inactive LED adjustment curve DC_(INACTIVE). The third and fourth LED duty cycles DC_(LED3), DC_(LED4) may be calculated using the inactive duty cycle curve DC_(INACTIVE) and/or the second LED duty cycle DC_(LED2). The active LED adjustment curve DC_(ACTIVE) and the inactive LED adjustment curve DC_(INACTIVE) may be stored in the memory 216.

FIGS. 4 and 5 illustrate example active and inactive adjustment curves DC_(ACTIVE), DC_(INACTIVE) for adjusting the duty cycle DC_(LED) of the LED current through each of the LEDs in response to the measured ambient light level L_(AMB). FIG. 4 shows an example active and inactive adjustment curves DC_(ACTIVE) and DC_(INACTIVE) on a linear scale, while FIG. 5 shows an example active and inactive adjustment curves DC_(ACTIVE) and DC_(INACTIVE) on a logarithmic scale. For example, if the measured ambient light level L_(AMB) is approximately 500 Lux, the first duty cycle DC_(LED1) of the LED current through the LED behind the control button having the active preset may be controlled to approximately 66%, while the second duty cycle DC_(LED2) of the LED current through each of the LEDs behind the control buttons having the inactive presets may be controlled to approximately 17%.

The human eye has a more difficult time discerning contrast in low ambient light levels than in high ambient light levels. Thus, the first duty cycle DC_(LED1) of the active adjustment curve DC_(ACTIVE) may be, for example, over ten times greater than the second duty cycle DC_(LED2) of the inactive adjustment curve DC_(INACTIVE) near a minimum ambient light level L_(AMB)-MIN (e.g., approximately 0 Lux), for example, as shown in FIGS. 4 and 5. Near a maximum ambient light level L_(AMB-MAX) (e.g., approximately 1000 Lux), the first duty cycle DC_(LED1) of the active adjustment curve DC_(ACTIVE) may be, for example, approximately three times greater than the second duty cycle DC_(LED2) of the inactive adjustment curve DC_(INACTIVE).

The active and inactive adjustment curves DC_(ACTIVE) and DC_(INACTIVE) are non-linearly related (e.g., not proportional), for example, as illustrated in FIGS. 4 and 5. The difference between the active and inactive adjustment curves DC_(ACTIVE) and DC_(INACTIVE) may be non-linear as the ambient light level ranges from the minimum ambient light level L_(AMB)-MIN to the maximum ambient light level L_(AMB)-MAX. The values of the active and inactive adjustment curves DC_(ACTIVE) and DC_(INACTIVE) may be chosen so that the button 104 having the text of the active preset may be visually distinguished (e.g., visually brighter) than the buttons 104 having the text of the inactive presets across a range of typical ambient light levels (e.g., between the minimum ambient light level L_(AMB-MIN) and the maximum ambient light level L_(AMB-MAX)). The values of the active and inactive adjustment curves DC_(ACTIVE) and DC_(INACTIVE) may also be chosen so that the text 120 on both the button 104 having the text of the active preset and the buttons 104 having the text of the inactive presets may be read across a range of typical ambient light levels (e.g., between the minimum ambient light level L_(AMB-MIN) and the maximum ambient light level L_(AMB-MAX)).

FIG. 6 is a simplified flowchart of an example backlighting procedure 400 that may be executed periodically by a control circuit (e.g., the control circuit 210) for backlighting a plurality of buttons of a control device (e.g., the buttons 104 of the keypad 100). The control circuit 210 may sample the ambient light detect signal V_(AMB) at 410. The control circuit 210 may determine the measured ambient light level L_(AMB) using the magnitude of the ambient light detect signal V_(AMB) at 412. The control circuit 210 may determine the first LED duty cycle DC_(LED1) from the active adjustment curve DC_(ACTIVE) (e.g., as shown in FIG. 4 or 5) using the measured ambient light level L_(AMB) at 414. The control circuit may determine the second LED duty cycle DC_(LED2) from the inactive adjustment curve DC_(ACTIVE) using the measured ambient light level L_(AMB) at 416. At 418, the control circuit 210 may set a selected-button number N_(SEL) to be equal to the presently selected button (e.g., the button having text indicating the active or selected preset or scene). During the backlighting procedure 400, the control circuit 210 may step through the LEDs 222 behind each of the buttons 104 and determine the correct LED illumination intensity for each of the buttons. The control circuit 210 may use a variable n for stepping through the LEDs during the backlighting procedure 400. At 420, the control circuit 210 may initialize the variable n to one.

If the variable n is equal to the selected-button number N_(SEL) at 422 (e.g., the present button is the selected button), the control circuit 210 may control the LED current conducted through the LED behind the selected button using the first LED duty cycle DC_(LED1) at 424. If the variable n is equal to the selected-button number N_(SEL) plus one at 426 (e.g., the button below the selected button), the control circuit 210 may calculate the third LED duty cycle DC_(LED3) at 428. For example, the control circuit 210 may calculate the third LED duty cycle DC_(LED3) based at least in part on the first predetermined amount of change Δ_(LED1) caused by the LED behind the selected button on the button below the selected button, e.g., DC_(LED3)=DC_(LED2)−(DC_(LED1)−DC_(LED2))·Δ_(LED1). At 430, the control circuit 210 may pulse-width modulate the LED current conducted through the LED behind the button below the selected button using the third LED duty cycle DC_(LED3).

If the variable n is equal to the selected-button number N_(SEL) minus one at 432 (e.g., the button above the selected button), the control circuit 210 may calculate the fourth LED duty cycle DC_(LED4) at 434. For example, the control circuit 210 may calculate the fourth LED duty cycle DC_(LED3) based at least in part on the second predetermined amount of change Δ_(LED2) caused by the LED behind the selected button on the button above the selected button, e.g., DC_(LED4)=DC_(LED2)−(DC_(LED1)−DC_(LED2))·Δ_(LED2).

At 436, the control circuit 210 may pulse-width modulate the LED current conducted through the LED behind the button above the selected button using the fourth LED duty cycle DC_(LED4). If the variable n is not equal to the selected-button number N_(SEL) minus one at 432, the control circuit 210 may pulse-width modulate the LED current conducted through the nth LED using the second LED duty cycle DC_(LED2) at 438. In one or more examples, if the variable n is not equal to the selected-button number N_(SEL) minus one at 432, the control circuit 210 may control the nth LED to an LED illumination intensity L_(LED) that is dependent upon the button's relative location with respect to the selected-button at 438.

After setting the LED illumination intensity at 424, 430, 436, and 438, the control circuit 210 may determine if the variable n is equal to a maximum number N_(MAX) (e.g., the number of buttons 104 on the keypad 100) at 440. If the variable n is not equal to the maximum number N_(MAX) at 440, the control circuit 210 may increment the variable n by one at 442, before the procedure 400 loops around the set the LED illumination intensity for the next LED. If the variable n is equal to the maximum number N_(MAX) at 440, the procedure 400 may simply exit. 

The invention claimed is:
 1. A control device comprising: a first button, a second button, and a third button; a first light source, a second light source, and a third light source, wherein the first, second, and third light sources are configured to illuminate at least a portion of a respective one of the first, second, and third buttons; and a control circuit responsive to actuations of the first, second, and third buttons, and electrically coupled to the first, second, and third light sources, the control circuit configured to: illuminate the first light source to a first source illumination intensity to illuminate first indicia on the first button; illuminate the second light source to a second source illumination intensity to illuminate second indicia on the second button; and illuminate the third light source to a third source illumination intensity to illuminate third indicia on the third button; wherein the second and third source illumination intensities are both less than the first source illumination intensity so that the first indicia on the first button is illuminated to a brighter intensity than the respective indicia on the second and third buttons; and wherein the second source illumination intensity is less than the third source illumination intensity in part because the second button is closer than the third button to the first indicia on the first button.
 2. The control device of claim 1, wherein the control circuit is configured to set the second and third source illumination intensities based on one or more preconfigured correction factors.
 3. The control device of claim 2, wherein the control circuit is configured to vary at least one of the correction factors based on the first, second, and third source illumination intensities.
 4. The control device of claim 2, wherein at least one of the correction factors is a constant percentage.
 5. The control device of claim 1, further comprising: an ambient light detector configured to generate an ambient light detect signal; wherein the control circuit is configured to receive the ambient light detect signal and to determine an ambient light level in a room in which the control device is installed based on the ambient light detect signal, and the control circuit is configured to control the first, second, and third source illumination intensities based on the ambient light level.
 6. The control device of claim 5, wherein the control circuit is configured to set the first source illumination intensity in dependence upon the ambient light level in the room based on an active adjustment curve, and set the second source illumination intensity and the third source illumination intensity in dependence upon the ambient light level in the room based on an inactive adjustment curve.
 7. The control device of claim 5, wherein the control circuit is configured to determine illumination caused by one or more of the first light source, the second light source, and the third light source, the control circuit further configured to determine the ambient light level in the room in which the control device is installed based on the ambient light detect signal and the illumination caused the one or more of the first light source, the second light source, and the third light source.
 8. The control device of claim 1, wherein the control circuit is configured to illuminate the first light source to the first source illumination intensity to illuminate the first indicia on the first button to approximately a first surface illumination intensity; illuminate the second light source to the second source illumination intensity and the third light source to the third source illumination intensity to illuminate the respective indicia on the second and third buttons to approximately a second surface illumination intensity.
 9. The control device of claim 8, wherein the control circuit is configured to detect degradation in the illumination intensity of the first light source, and compensate for the degradation in the first light source by increasing the first source illumination intensity to illuminate the first button to approximately the first surface illumination intensity.
 10. The control device of claim 1, wherein the first, second, and third light sources comprise light-emitting diodes.
 11. A method of backlighting buttons of a control device, the control device comprising first, second, and third buttons, and first, second, and third light sources positioned to illuminate a respective one of the first, second, and third buttons, the method comprising: illuminating the first light source to a first source illumination intensity to illuminate first indicia on the first button; illuminating the second light source to a second source illumination intensity to illuminate second indicia on the second button; illuminating the third light source to a third source illumination intensity to illuminate third indicia on the third button; wherein the second and third source illumination intensities are both less than the first source illumination intensity so that the first indicia on the first button is illuminated to a brighter intensity than the respective indicia on the second and third buttons; and wherein the second source illumination intensity is less than the third source illumination intensity in part because the second button is closer than the third button to the first indicia on the first button.
 12. The method of claim 11, further comprising: determining an ambient light level in a room in which the control device is installed; and adjusting the first source illumination intensity, the second source illumination intensity, and the third source illumination intensity based on the ambient light level.
 13. The method of claim 12, further comprising: increasing the first source illumination intensity, the second source illumination intensity, and the third source illumination intensity in response to detecting an increase in the ambient light level; and decreasing the first source illumination intensity, the second source illumination intensity, and the third source illumination intensity in response to detecting a decrease in the ambient light level.
 14. The method of claim 12, further comprising: setting the first source illumination intensity in dependence upon the ambient light level in the room based on an active adjustment curve; and setting the second source illumination intensity and the third source illumination intensity in dependence upon the ambient light level in the room based on an inactive adjustment curve.
 15. The method of claim 12, wherein determining the ambient light level comprises measuring light in the vicinity of the control device and removing illumination caused by at least one of the first light source, the second light source, or the third light source to determine the ambient light level.
 16. The method of claim 11, further comprising: setting the second and third source illumination intensities based on one or more preconfigured correction factors.
 17. The method of claim 16, further comprising: varying at least one of the correction factors based on the first, second, or third source illumination intensities.
 18. The method of claim 16, wherein at least one of the correction factors is a constant percentage.
 19. The method of claim 11, further comprising: illuminating the first light source to the first source illumination intensity to illuminate the first indicia on the first button to approximately a first surface illumination intensity; illuminating the second light source to the second source illumination intensity to illuminate the second indicia on the second button to approximately a second surface illumination intensity; and illuminating the third light source to the third source illumination intensity to illuminate the third indicia on the third button to approximately the second surface illumination intensity.
 20. The method of claim 19, further comprising: detecting degradation in the illumination intensity of the first light source; and compensating for the degradation in the first light source by increasing the first source illumination intensity to illuminate the first button to approximately the first surface illumination intensity. 